Method and system for measuring pulmonary artery circulation information

Abstract

Minimally invasive systems and methods are described for measuring pulmonary circulation information from the pulmonary arteries. A transbronchial Doppler ultrasound catheter is advanced through the airways and in the vicinity of the pulmonary artery. Doppler ultrasound energy is sent through the airway wall and across the pulmonary artery to obtain velocity information of blood flowing through the artery. The velocity information is used to compute pulmonary circulation information including but not limited to flowrate.

1. A transbronchial medical system for measuring pulmonary circulation information of the pulmonary artery from the bronchi and without penetrating the pulmonary artery during a live procedure comprising:
 a transbronchial catheter comprising a flexible shaft and a distal section, said distal section comprising at least one ultrasonic transducer; and 
 an ultrasound Doppler signal processing unit comprising: 
 an output port for delivering outgoing electrical signals to said at least one ultrasonic transducer; 
 an input port for receiving incoming electrical signals from said at least one ultrasonic transducer; 
 a processor in communication with said output port and said input port and configured (a) to control the outgoing electrical signals delivered to said ultrasonic transducer; (b) to receive and analyze the incoming electrical signals for volumetric flowrate (Q) of the pulmonary artery using Doppler shifting and time of flight analysis; (c) to determine a precursor pressure signature of the fluid in the pulmonary artery using Doppler shifting; and (d) to identify a pulmonary arterial pressure (PAP) by comparing said precursor pressure signature to a database of pressure signatures determined prior to the live procedure wherein each of said predetermined pressure signatures has a corresponding mean pulmonary arterial pressure determined prior to the live procedure. 
 
     
     
       2. The system of  claim 1  wherein said catheter comprises a longitudinal axis, and said at least one ultrasonic transducer comprises a first transducer having a first angle with respect to said axis of said catheter, and a second transducer having a second angle with respect to said axis of said catheter and said first angle and said second angle are different. 
     
     
       3. The system of  claim 1 , wherein said processor is further configured to calculate a TPR ratio where the TPR ratio is proportional to PAP and inversely proportional to Q. 
     
     
       4. The system of  claim 2 , wherein the outgoing and incoming ultrasonic signals are analyzed to determine velocity (V) and a diameter (D) of the pulmonary artery, and further determining Q based on V and D. 
     
     
       5. The system of  claim 1  further comprising a bronchoscope through which said catheter is inserted. 
     
     
       6. The system of  claim 4  further comprising a visual display adapted to display at least one of V and Q. 
     
     
       7. A method for determining pulmonary circulation information in a pulmonary artery of a patient during a live procedure without puncturing or opening the pulmonary artery, said method comprising:
 providing an ultrasound Doppler catheter, said catheter comprising a distal section and at least one ultrasound transducer in said distal section; 
 advancing said distal section of said ultrasound Doppler catheter through a natural respiratory opening of the patient, and into an airway and to a location along an airway wall such that at least a portion of said distal section and said at least one ultrasound transducer is in proximity of the pulmonary artery; 
 sending and receiving ultrasonic waves to said pulmonary artery from said ultrasound transducer; 
 determining a measured pressure signature by analyzing the received ultrasonic waves; and 
 comparing the measured pressure signature to a database created prior to the live procedure, said database comprising one or more predetermined pressure signatures wherein each of said predetermined pressure signatures has an associated mean pulmonary arterial pressure measured prior to the live procedure. 
 
     
     
       8. The method of  claim 7  wherein the one or more predetermined pressure signatures and associated mean arterial pressure are determined based on empirical data arising from directly measuring the mean pulmonary arterial pressure in a blood vessel of a participant subject with a sensor for a plurality of different precursor pressure signatures. 
     
     
       9. The method of  claim 1  wherein the corresponding mean pulmonary arterial pressure was determined using a standard PAP measurement technique. 
     
     
       10. The method of  claim 9  wherein the standard PAP technique is a right heart catheterization. 
     
     
       11. A transbronchial method for determining flowrate in a blood vessel in the thoracic cavity during a live procedure, said method comprising the steps of:
 providing an ultrasound catheter, said catheter comprising a distal section and at least one ultrasound transducer in said distal section; 
 advancing said distal section of said catheter through a natural respiratory opening, and into an airway such that at least a portion of said distal section and said at least one ultrasound transducer is in proximity of the blood vessel; 
 sending ultrasound energy along a path across a tissue region, said tissue region including said blood vessel; and 
 analyzing reflected ultrasound energy to determine flowrate in said blood vessel wherein said analyzing comprises comparing a measured pressure signature to a database created prior to the live procedure, said database comprising one or more predetermined pressure signatures wherein each of said predetermined pressure signatures has an associated mean pulmonary arterial pressure measured prior to the live procedure. 
 
     
     
       12. The method of  claim 11  wherein said analyzing comprises determining an instantaneous velocity profile across the tissue region, and computing an instantaneous flowrate in the blood vessel based on said instantaneous velocity profile. 
     
     
       13. The method of  claim 12  wherein said instantaneous flowrate is calculated by, at least in part, computing a plurality of component flowrates corresponding to a plurality of discrete area cross sections across the tissue region. 
     
     
       14. The method of  claim 13 , wherein the discrete area is annulus. 
     
     
       15. The method of  claim 14  further comprising identifying the center of the blood vessel prior to determining the step of computing a plurality of component flowrates. 
     
     
       16. The method of  claim 11  further comprising determining a temporal flowrate by obtaining a plurality of instantaneous flowrates over a sampling duration and time-averaging said instantaneous flowrates over said sampling duration. 
     
     
       17. The method of  claim 16  wherein said sampling duration is between 6 to 10 seconds. 
     
     
       18. The method of  claim 14  wherein said analyzing step is based at least in part on a slant angle, said slant angle equal to an angle formed between the distal end of said catheter and a normal vector, said normal vector being normal to a central axis of the blood vessel. 
     
     
       19. The method of  claim 11  wherein said ultrasound catheter operates using a sampling range sufficient to detect zero velocity in tissue proximal and distal to the blood vessel, and said sampling range being greater than the diameter of the blood vessel. 
     
     
       20. The method of  claim 11  wherein said flowrate is determined without measuring an actual diameter of the blood vessel. 
     
     
       21. The method of  claim 11 , wherein the blood vessel is a pulmonary artery, and further comprising determining a mean PAP in the pulmonary artery, wherein said mean PAP is determined using ultrasonic waveform analysis and comprises comparing a measured pressure signature to a predetermined pressure signature. 
     
     
       22. The method of  claim 21  further comprising calculating a TPR.